This invention relates to programmable controllers and more specifically to an input/output system therefor.
In most prior art programmable controllers, the input/output systems are generally constructed in a manner which requires the equipment connected thereto to be disconnected whenever a panel is removed, replaced, or in any way rearranged. As a result, an expensive, time-consuming effort is required to accomplish the necessary maintenance and field wiring.
Another problem common with most prior art programmable controllers is the necessity for shutting down the entire controller whenever an individual input/output circuit needs to be replaced or repaired. Similarly, this type of construction produces excessive down-time and increased burden on replacing and removing the input/output circuits. Furthermore, the input and output circuits are typically fixed with a particular address that is not easily changed.
The best prior art patent, of which we are aware, is U.S. Pat. No. 3,942,077 of Howard A. Powers. In Powers, a modular panel construction for an input/output assembly is disclosed which eliminates many previous prior art problems. In Powers, interconnecting input/output panel housings are employed with each panel housing accepting up to four removable input/output modules. Furthermore, the input/output modules are capable of being directly plugged into the input/output panel housing and have fixed terminals to which external equipment is connected. In this way, the necessity for disconnecting and reconnecting external equipment wiring during removable or replacement of the input/output modules is eliminated.
In spite of the advance made by Powers, the modular panel construction disclosed therein suffers from various difficulties which have heretofore remained unresolved. Some of these difficulties include input/output modules which are heavy and cumbersome to use, and require supporting tracks and camming systems to assure secure and complete interconnection of the input/output module with the input/output panel housing. As a result, ease of handling and speed of installation and removal of the modules is hampered.
Additionally, the connectors of Powers between the input/output modules and the input/output housing were fixed and located in readily inaccessible positions. Consequently, any connector failure required the complete disassembly of the input/output system, removal of the connectors, and resoldering of new connectors to the I/O housings.
Therefore, it is a principal object of this invention to provide an input/output assembly for a programmable controller which incorporates a lightweight, easily handled, input/output module capable of quick and easy insertion, removal and replacement without necessitating removal of the external devices wired thereto.
Another object of this invention is to provide an input/output assembly for a programmable controller having the characteristic features defined above wherein the input/output module can be inserted and connected to the input/output housing at an angle and swung into interconnected engagement with an external device wiring strip.
Another object of this invention is to provide an input/output assembly for a programmable controller having the characteristic features defined above which is capable of complete removal and replacement of all connectors without soldering, thereby assuring easy and reliable field maintenance.
A further object of the present invention is to provide an input/output assembly for a programmable controller having the characteristic features defined above which also provides protection against electromagnetic interference without requiring the use of shielded cables.
Another object of the present invention is to provide an input/output assembly for a programmable controller having the characteristic features defined above which also provides for quick and easy interconnection of external device wiring having up to two number 12 wires per connection point.
Another object of the present invention is to provide an input/output assembly for a programmable controller having the characteristic features defined above wherein the address for the input/output housing can be individually set for each input/output housing prior to interconnection with the central processing unit.
Other objects of the invention will in part be obvious and will in part appear hereinafter.